[Association between 25-hydroxyvitamin D levels and cognitive performance in middle-aged and older European men J Neurol Neurosurg Psychiatry 2009; doi 10.1136/jnnp.2008.165720]

Vitamin D may have a key role in helping the brain to keep working well in later life, suggests research published ahead of print in the Journal of Neurology Neurosurgery and Psychiatry.

Previous research indicates that inadequate vitamin D intake may be linked to poorer mental agility in the ageing brain, but the results have been inconsistent.

The researchers base their current findings on just over 3000 European men between the ages of 40 and 79, who were all part of the international European Male Ageing Study, drawn from eight different cities across Europe.

Their mental agility was assessed using a range of tests, designed to measure memory and speed of information processing as well as mood and physical activity levels, both of which affect mental agility.

Blood samples were then taken to measure circulating levels of vitamin D, which is obtained through dietary sources and by exposure to sunlight.

High circulating vitamin D levels were associated with high scores on the memory and information processing tests, but after adjusting for mood and physical activity, the association remained for only one of the two information processing tests.

Low vitamin D levels were associated with poor scores, with levels of 35 nmol/litre or under marking the threshold of poorer performance.

Experimental data point to the biological plausibility for an association between low circulating levels of vitamin D and poorer mental agility, but exactly how the two might be connected is not clear, say the authors.

Possible suggestions include vitamin D's role in increasing certain hormonal activity or the protection of neurones and chemical signalling pathways.

The findings show that the magnitude of the association between vitamin D level and mental agility was comparatively small, say the authors.

But if it were possible to stave off the effects of ageing on the brain with vitamin D supplements, then the implications for population health could be quite significant, they contend, because many people, particularly in older age, are vitamin D deficient.

Journal Of Neurology Neurosurgery And Psychiatry